Heater



FIG. 1 is a front elevation view of a heater showing our new design;

FIG. 2 is a right side elevation view thereof;

FIG. 3 is a rear elevation view thereof;

FIG. 4 is a left side elevation view thereof;

FIG. 5 is a top plan view thereof; and,

FIG. 6 is a bottom plan view thereof.

The ornamental design for a heater, as shown.